Fix for memory leak in RSA-SSA signing

Fix in mbedtls_rsa_rsassa_pkcs1_v15_sign() in rsa.c. Resolves github issue #372
diff --git a/ChangeLog b/ChangeLog
index f306742..2a81894 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,8 @@
    * Fix bug in certificate validation that caused valid chains to be rejected
      when the first intermediate certificate has pathLenConstraint=0. Found by
      Nicholas Wilson. Introduced in mbed TLS 1.3.15. #280
+   * Removed potential leak in mbedtls_rsa_rsassa_pkcs1_v15_sign(), found by
+     JayaraghavendranK. #372
 
 = mbed TLS 1.3.15 released 2015-11-04